Preheat the oven to 350F.
Place the olive oil in a skillet, over medium heat. Add the onions and cook for about 5 minutes or until translucent.
Add the mushrooms, thyme, salt and pepper. Cook for about 7 to 9 minutes. Set aside.
In a medium bowl place the flour and baking powder. Set a side.
In a another bowl place the milk, cream cheese, ricotta, cheddar, olive oil, eggs and parmesan cheese. Mix well until combined.
Add the flour mixture to the milk mixture and mix well, add the mushrooms reserving some for garnish.
Season with salt and pepper and stir until well combined. Pour the mixture onto a greased baking pan. Top with the reserved mushrooms and parmesan cheese. Bake for 45 minutes or until ready. Let it cool before removing.